Hydraulic circuit for control of earthmoving scraper bowls



A ril 7, 1964 A. J. HElN ETAL HYDRAULIC CIRCUIT FOR CONTROL OFEARTHMOVING SCRAPER BOWLS 3 Sheets-Sheet 1 Filed Dec. 26, 1962INVENTORS. ALLYN J. HEW JAMEs ESCHEHJT AT ORNEYS April 7, 1964 A. J.HElN ETAL HYDRAULIC CIRCUIT FOR CONTROL OF EARTI-IMOVING SCRAPER BOWLS 3Sheets-Sheet 2 Filed Dec. 26, 1962 INVENTORS. ALLYN J. HE! N BY JAM ESE. SCH E. DT

A ORN-EYS A ril 7, 1964 A. J. HEIN ETAL 3,127,633

HYDRAULIC CIRCUIT FOR CONTROL OF EARTHMOVING SCRAPER BOWLS Filed Dec.26, 1962 3 Sheets-Sheet 5 INVENTORS. ALLYN J. Ham BYJAMES EScHEwT 9 w 1ATTORNEYS United States Patent M 3,127,688 HYDRAULIC CHRUUHT FOR CONTROLOF EARTHMUVENG RAPER BUWLS Allyn J. Hein and lames E. Ssheidt, Juliet,Ill., assignors to Caterpillar Tractor (10., Peoria, lll., a corporationof California Filed Dec. 26, 1962, Ser. No. 247,056 3 Claims. (ill.3'7129) This invention relates to tractor drawn earthmoving scraperswherein various elements and particularly the bowl of the scraper isadjusted by means of double acting hydraulic jacks and pertainsspecifically to means for preventing accidental quick lowering of thebowl.

' The hydraulic circuit of the present invention is an improvement onthe circuit disclosed in the Allyn J. Hein et al. Patent No. 3,868,596for Hydraulic Circuit for Actuation of an Earthmoving Scraper Bowl. Thesaid Hein et al. patent discloses two valves in a bowl jack circuitincluding a load supporting check valve which prevents escape of fluidfrom the jack when it is supporting a load elevated with respect to theearth. This prevents the weight of the load from imposing high fluidpressures in the conduits and hoses which connect the jack supported onthe scraper with the control valve supported on the tractor.

A second or quick drop valve is assocated w-tih each of the bowl liftjacks normally closing communication between the head end of the jackand the rod end of the jack but adapted to be opened to-permit suchcommunication in order to effect quick lowering or dropping of the bowlfrom a raised position. This quick drop valve is held in its closedposition by fluid pressure vented through a line communicating betweenthe scraper and the control valve on the tractor. The line is,therefore, subject to breakage in operation and failure of the linewould vent pressure holding the quick drop valve closed creating ahazardous condition because dropping of the bowl from a carry positionwhile the tractor and scraper are traveling at high speed could cause asudden stop that would throw the operator from his seat.

It is the object of the present invention to overcome the aforementioneddisadvantages and hazard and to provide a circut for actuating a scraperbowl or the like including a quick drop valve adapted to be opened uponintentional venting of its closing pressure but incapable of beingopened by accidental venting of such pressure as will occur upon leakageor failure of the vent line.

Further and more specific objects and advantages of the invention areset forth in the following specification wherein the invention isdescribed in detail by reference to the accompanying drawings.

In the drawings:

FIG. 1 is a schematic view of the hydraulic circuit for atractor-scraper combination which includes bowl, ejector and apronactuating jacks;

FIG. 2 is a schematic sectional view of one of the bowl lift jacks shownin FIG. 1 including the valve mecha nism associated therewith foraccomplishing the objects of the present invention; and

FIG. 3 is a side elevation of a tractor-scraper combination illustratingthe location of the several components of the hydraulic circuit whichcontrol the operation of adjustable elements of the scraper.

In FIG. 3, a conventional two-wheel scraper is illus- 3,1127,688Patented Apr. 7, 1964 trated at 10 as drawn by a tractor 11 through ahitch or draft connection generally indicated at 12. The main body orbowl of the scraper may be raised and lowered about its pivotalconnection with its wheels 13. Draft arms 14 pivoted to opposite sidesof the scraper bowl as by connections, one of which is shown at 15,enable raising and lowering of the scraper bowl by means of a pair ofjacks, one of which is shown at 16. A pivoted apron 17 is adapted to beraised and lowered for opening and closing the forward end of the bowlby means of a jack 18, lever 18b and link 18c and an ejector 19 is movedforwardly to discharge the contents of the bowl through its forward endby an ejector jack 2%), all in it well known manner. A control valveassembly 22 for controlling the flow of fluid to and from the severaljacks is disposed on the tractor as are also control levers, one shownat 23 positioned adjacent the operators station.

The hydraulic circuits disclosed in FIG. 1 of the drawings are,generally speaking, the same as those disclosed in the above mentionedHein et al. patent and will be briefly described herein to facilitate anunderstanding of the present invention.

The control valve assembly, generally indicated at 22 in FIG. 1,comprises a single housing suitably bored for the reception of threesliding type valve spools 16a, 18a and Zita for controlling jacks l6, l8and 2% which actuate respectively the scraper bowl, apron and ejector.Each of the spools is formed at one end for connection to controllevers, not shown, and is fitted at its opposite end with a centeringspring assembly shown at 26, 21; and 36. The function of such assemblyis well known and only that pertaining to the bowl lift control is shownin detail and will be hereinafter described.

A pump 35 delivers fluid under pressure from a reservoir 36 to an inletpassage 37 in the valve housing which is divided to direct fluidselectively toward either end of the valve spool 16a depending upon itsposition of adjustment. Similar inlet passages 38 and 39 communicatewith each other and with the first pasage 37 so that with the valvespools in their neutral positions, as shown, there is a constant flow offluid under pressure from the pump through the passageways 37, 38 and 39and a discharge passage 40 and thence back to the reservoir through areturn line 41. A relief valve 42 in the pressure line from the pumpalso has its'discharge side connected with the return line 41.

Each of the jacks or sets of jacks has what may be termed a highpressure and a lower pressure end because the work of moving animplement part in one direction as when it is being raised or movingearth is usually greater than that of moving it in the other direction.Movement of any one of the spools to the right connects it with the highpressure end of its associated jack. For example, the spool 16a uponmovement toward the right opens communication with the inlet chamber 37containing fluid under pressure from the pump and directs the fluid intoa line 46 and through lines 46a to the rod ends of the jacks 16 forraising the bowl. Similarly movement of spools 18a to the right connectsthe inlet passage 38 thereof with a line 48 connecting with the head endof the jack 1-8 through a valve mechanism 64 and movement of spool 219ato the right directs fluid under pressure from inlet 3? through a line50 to the head end of the ejector jack 20. The

construction of the valve mechanism 64 is not necessary to anunderstanding of the present invention.

The opposite or low pressure ends of the jaoks are all connected with acommon manifold 52 which communicates with each of the three borescontaining the valve spools and is opened by rightward movement of anyspool into communication with a discharge manifold 53, also common toall three spools and communicating with the reservoir through the line41. Consequently when fluid is directed under pressure to the highpressure side of any of the jacks, fluid on the low pressure side isreturned to the reservoir. The common manifold 52 is connected with thejacks through a common line 54 with a branch 55 to the low pressure orhead ends of the bowl jacks 1 6, a branch 56 to the rod end of theejector jack 2t} and a branch 57 to the rod end of the apron jackthrough the valve mechanism 64'.

Movement of the jacks in the direction opposite to that described aboveis accomplished by movement of any one of the valve spools in theopposite direction or to the left which communicates high pressurethrough the actuated spool to the manifold 52 and thence to all of thejacks through line 54 and its branches 55, 56 and 57. The valve spoolwhich has been actuated to the left also opens communication to adischarge passage 68 which is common to all or the spools and similar tothe discharge passage 53. The discharge passage 60 permits return offluid from the jack which has been actuated through the passage 46 andline 51 to the reservoir. Under the condition just described where asingle valve spool is actuated and directs fluid to all three jacks,only the selected jack is moved because return flow from the other jacksis blocked by their respective spools which have remained in theirneutral position.

Pressure in the conduits communicating between the bowl jacks 16 on thescraper and the control valve on the tractor is relieved while the bowlis held in a raised position so that the lines are protected againstexcessive pressure resulting from the dynamic action of the weight ofthe bowl and its contents when being transported over rough terrain.This is accomplished by a check valve 65, see FIG. 2, in a housing 66associated one with each of the jacks 16. This check valve is urgedtoward its closed position by a spring 67 and is opened by pressure fromthe pump entering the rod end of the jack through the line 46 duringraising of the bowl. With the check valve open, the fluid under pressurepasses through the line 46a to the rod end of the jack. When the bowl isheld in a raised position, the check valve is closed by the spring 67,the force of which is augmented by fluid pressure within the springchamber entering through orifices 68 in the valve element.

Pressure in the spring chamber of the check valve 65 is reduced when itis desired to lower the bowl and this is accomplished through a line 72communicating between the spring chamber and a passage 73 (see FIG. 1)which upon movement of the spool 16a. to the left for lowering the bowl,will communicate with a groove 74 in the spool 16a and through thisgroove with a second passage 75 in the valve housing, and a bleed line76 communicating between the passage 75 and the reservoir. With fluidpressure thus reduced in the spring chamber 67, pressure in line 4611,due to weight of the bowl, becomes effective to open the check valve 65and permit return of fluid from the rod end of jack 16 through the line46 as previously described. This is accomplished by a pilot piston 78with an end 79 engageable with the check valve when it is in its closedposition. Pressure from the rod end of the jack is communicated througha passage 88 to the interior of the pilot piston 78 moving it to theright as viewed in FIG. 2 and opening the check valve against theclosing force of spring 67.

To provide for dropping or lowering of the bowl at a rate in excess ofthat resulting from normal operation of the control valve for moving thebowl toward its lowered position, a quick drop valve 86 is contained inthe housing 66. This valve closes communication between the head end androd end of the jack by way of a line 55a, passage 88 and line 46a. Whenthe valve 86 is opened, as by movement toward the right as viewed inFIG. 2, flow from the rod end to the head end of the jack permits rapiddownward movement of the piston due to the weight of the bowl and itscontents and without evacuating the head end of the jack. The check orquick drop valve is urged toward its closed position by a spring 8 9acting against a pilot piston 96 slidable in the valve bore and abuttingthe valve as shown. The pressure of the spring 89 is augmented by fluidpressure communicated from the line 46 through a passage 91 in the valvehousing and communicating with the spring chamber. The pilot pistonprevents opening of the quick drop valve when the pressure in passage 88is less than the pressure in line 46 and the spring chamber. When it isdesired to permit the valve 86 to open under pressure of fluid in theline 46a, the pressure in the spring chamber is vented through a line95. This line, as shown in FIG. 1, communicates with a passage 96 in thecontrol valve housing adjacent the bleed passage 73 previously describedand can be opened by movement of the spool 16a toward the left beyondits bowl lowering position. This further movement of the spool 16a.toward the left provides communication between the passage 96 and thepassage 75 so that pressure in the chamber of spring 89 (FIG. 2) isrelieved through the line 76 to the reservoir. Pressure for opening thevalve 86 is admitted to its face through orifices 92 in a cup-shapedstop member and fluid flows through orifices 93 in the valve body.Meanwhile the spool 1611 having been moved to its bowl loweringposition, the chamber of its spring 67 has been vented through the line72 and pressure in pilot piston 78 has opened the check valve.

A spring 98 in the centering spring assembly 26 is used in addition tothe conventional centering spring which is shown at 99. When thecentering spring 99 is com pressed by movement of the spool to its bowllowering position, a flange 1% on the spring seat engages an amin lus101 which serves as a seat for the heavier spring 98 providing a stopwhich can be sensed by the operator. Further leftward movement of thespool is accomplished only by greater operator eflort sufficient tocompress the spring 98.

It is to be understood that the check valves associated with the jacks16 as well as the bleed lines associated with them are identicalfor bothof the bowl jacks. In order to insure balanced pressure in the rod endsof the two jacks, the valve housings 66 are interconnected by a smallline 105 which, as shown in FIG. 2, forms communication between thelines 46a which communicate with the rod ends of the jacks.

Due to the construction described above wherein the load supportingcheck valve is disposed intermediate the jack 16 and the quick dropvalve, the load supporting valve serves in its normally closed conditionto prevent flow of fluid from the rod end to the head end of thecylinder. Consequently leakage or breaking of the line which permitsopening of the quick drop valve will not result in accidental droppingof the bowl.

We claim:

1. In combination with a tractor drawn earthmoving scraper having abowl, a hydraulic circuit, means supplying fluid under pressure to saidcircuit, a double acting hydraulic jack in said circuit for raising andlowering the bowl, and means in said circuit including a control valveon the tractor for directing fluid to said jack, a fluid pas sagebetween the head and rod ends of the jack a quick drop valve in saidpassage preventing flow between the head end and rod end of said jack,means normally communicating fluid under pressure to said quick dropvalve 3. The combination of claim 2 in which the control to hold itclosed, means to vent said fluid to permit openvalve etfects opening ofthe quick drop valve and the load ing of the valve, and a loadsupporting check valve dissupporting check valve upon movement beyond anormal posed in the circuit between the cylinder and the quick bowllowering position. drop valve to prevent accidental bowl drop uponleakage 5 of said venting means. References Cited in the file of thispatent 2. The combination Of claim 1 in which the venting UNITED STATESPATENTS means 1s assoclated with the control valve on the tractor,2,897,613 Davidson Aug. 4, 1959 and means to effect opening of the loadsupporting check valve upon actuation of the venting means. 10

1. IN COMBINATION WITH A TRACTOR DRAWN EARTHMOVING SCRAPER HAVING ABOWL, A HYDRAULIC CIRCUIT, MEANS SUPPLYING FLUID UNDER PRESSURE TO SAIDCIRCUIT, A DOUBLE ACTING HYDRAULIC JACK IN SAID CIRCUIT FOR RAISING ANDLOWERING THE BOWL, AND MEANS IN SAID CIRCUIT INCLUDING A CONTROL VALVEON THE TRACTOR FOR DIRECTING FLUID TO SAID JACK, A FLUID PASSAGE BETWEENTHE HEAD AND ROD ENDS OF THE JACK A QUICK DROP VALVE IN SAID PASSAGEPREVENTING FLOW BETWEEN THE HEAD END AND ROD END OF SAID JACK, MEANSNORMALLY COMMUNICATING FLUID UNDER PRESSURE TO SAID QUICK DROP VALVE TOHOLD IT CLOSED, MEANS TO VENT SAID FLUID TO PERMIT OPENING OF THE VALVE,AND A LOAD SUPPORTING CHECK VALVE DISPOSED IN THE CIRCUIT BETWEEN THECYLINDER AND THE QUICK DROP VALVE TO PREVENT ACCIDENTAL BOWL DROP UPONLEAKAGE OF SAID VENTING MEANS.